This study involves determination of some fundamental functional processes at the tissue and cellular level in female reproductive organs during the periods of functional maturity and senile decline. Studies include ovarian steroid secretion, ovulation, uterine uptake and metabolism of steroids and uterine reactivity at different ages. Both in vivo and in vitro studies are being done. Histological, histochemical, biochemical and physiological studies on the various tissues and cells are being done. Estrogen and progesterone receptors in young and old and their changes under the varying hormonal influences are being studied. Of particular interest are the factors which show changes which cause the older females to be less efficient in their reproductive performance to the extent that there is a cessation of ability to bear young long before the ovary runs out of oocytes or ceases to ovulate and secrete its hormones. Since uterine function appears to be an important element in this senile decline, we are concentrating more effort on this tissue.